Alpha-cyanophenylacetic acid developing agents

ABSTRACT

NOVEL SILVER HALIDE DEVELOPING AGENTS COMPRISING ALPHACYANOPHENYLACETIC ACIDS DERIVED FROM ESTER PRECIRSORS BY ALKALI HYDROLYSIS ARE USED IN PHOTOGRAPHIC DIFFUSION TRANSFER SYSTEM.

United States Patent Office 3,795,518 Patented Mar. 5, 1974 ABSTRACT OF THE DISCLOSURE Novel silver halide developing agents comprising alphacyanophenylacetic acids derived from ester precursors by alkali hydrolysis are used in photographic diffusion transfer systems.

This invention relates to photography and more particularly to compositions and processes useful in the development of photosensitive silver halide elements.

One object of the present invention is to provide novel compositions and processes useful in developing exposed photosensitive silver halide elements. Other objects will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation and order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

It has now been discovered that basic solutions of compounds containing the functional grouping H o J ll oH AEN joined to a benzene ring effectively develop latent images present in exposed photosensitive silver halide elements. Alkali hydrolyzable esters of these alpha-cyanophenylacetic acids serve as useful precursors in the development process. Illustrative of such acids and esters are those represented by the formula:

1 H a) B1 -iJ-Rz EN Rt wherein each R is selected from hydrogen, methyl, methoxy, chloro and nitro groups and R is selected from hydroxy and alkoxy groups.

It will be appreciated that the above compounds may contain substituents other than those specified, e.g., chromophoric groups or groups limiting diffusion, provided the stated functional grouping is present or is formed during processing. Obviously any such substituent should not be antagonistic to the photographic process. Both the substituted and unsubstituted forms of these acids and esters are known and may be prepared by known procedures; see, for example, De Jongh et al., J. Org. Chem., v. 36, pp. 3160-3168 (1971).

As reported in the literature, oxidation of compounds such as these produces dimers, e.g.,

It is readily apparent that such oxidation of an alphacyanophenylacetic acid developing agent greatly reduces both its solubility and diifusi'bility, the former resulting from loss of the carboxyl group and the latter from the increased bulk of the dimerized product. These two properties, which help to confine oxidized developing agent in developed areas of the photosensitive element, are most advantageous in the photographic process. For example, an oxidized developing agent which is colored can provide a colored image in situ with the developed silver image. If difiusion transfer techniques are employed, these properties reduce stain in positive areas of the transfer image. Furthermore, such alpha-cyanophenylacetic acids are more efficient developing agents, requiring only two electrons in the development process.

The following examples are intended to further illustrate the invention but not to limit its scope.

EXAMPLE 1 A solution containing the following materials was mixed at room temperature: 0.156 g. of alpha-cyanophenylacetic acid, 0.470 g. of anhydrous sodium sulfite, 10 ml. of 0.5 molal sodium hydroxide and enough water to make 30 ml. of solution. This solution was used to develop an orthochromatic, low speed, high contrast film sold by Eastman Kodak under the designation Contrast Process Ortho film (Kodak CPO). It was found to give discriminatory development, slower than a hydroquinone solution in development rate and with comparable discrimination. The hydroquinone solution was prepared by mixing at room temperature: 0.060 g. of hydroquinone, 0.462 g. of anhydrous sodium sulfite, 10 ml. of 0.5 molal sodium hydroxide and enough water to make 30 ml. of solution.

EXAMPLE 2 Equal volumes of the alpha-cyanophenylacetic acid and hydroquinone developing solutions described in Example 1 were mixed together at room temperature. The same type of film utilized in Example 1 was developed, giving an image which exhibited increased delta density, i.e., a greater difference between maximum and minimum densities as compared with the novel developing agent alone-The developer solution in this example and in Example 1 gave discriminatory development even without an antifoggant. Of course the addition of an antifoggant markedly increases the difference between maximum and minimum densities.

EXAMPLE 3 A developing solution similar to that described in Example 1 was prepared using ethyl alpha-cyanophenyl acetate instead of the free acid. The solution was allowed to stand prior to its use in developing a fogged silver halide emulsion. Analysis of the developing solution confirmed that the active agent was the carboxylic acid produced by alkali hydrolysis of the ester precursor.

These examples clearly indicate that alpha-cyanophenylacetic acids and esters may be used alone or in conjuction with other silver halide developing agents. The usual developer composition components, e.g., antifoggants, silver halide solvents, restrainers, accelerators, etc., may of course be included where appropriate. Concentrations of these components and of the developing agents can be varied as necessary or desired.

The developing agents disclosed herein may be initially positioned in the photographic fihn, e.g., in, on or behind the silver halide containing layer, and activated by application of a processing composition which provides the requisite alkalinity. They are useful in dye and silver diffusion transfer processes, as well as in conventional multistage and multibath procedures to obtain both color and black and white photographs. Other materials, e.g., diffusion transfer thickeners, may be added in accordance with the processing techniques employed.

Since certain changes may be made in the above product without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A method of developing a silver halide emulsion which comprises processing an exposed photosensitive element containing a layer of said emulsion with an aqueous alkaline solution containing a hydroquinone silver halide developing agent and a cyano silver halide developing agent having the developing function:

1 1 -c- --on bonded to a benzene ring.

2. The method of claim 1 wherein said cyano silver halide developing agent is of the formula:

agile].

(JEN

wherein each R is selected from hydrogen, methyl methoxy, chloro and nitro groups.

3. The method of claim 2 wherein said cyano silver halide developing agent is alpha-cyanophenylacetic acid. 4. A method of developing a silver halide emulsion which comprises:

(a) treating an alkali hydrolyzable ester precursor of a cyano silver halide developing agent having the developing function:

H 0 n d-ii-on wherein each R is selected from hydrogen, methyl, methoxy, chloro and nitro groups.

6. The method of claim 5 wherein said cyano silver halide developing agent is alpha-cyanophenylacetic acid and said ester precursor is ethyl alpha-cyanophenyl acetate.

7. A photosensitive element comprising a support carrying a photosensitive silver halide emulsion layer, a hydroquinone silver halide developing agent and a cyano silver halide developing agent having the developing function:

8. The photosensitive element of claim 7 wherein said cyano silver halide developing agent is of the formula:

m-Qi-E-on R EN wherein each R is selected from hydrogen, methyl, methoxy, chloro and nitro groups.

9. The photosensitive element of claim 8 wherein said silver halide developing agent is alpha-cyanophenylacetic acid.

10. The photosensitive element of claim 7 wherein said cyano silver halide developing agent is positioned in said silver halide emulsion layer.

11. The photosensitive element of claim 7 wherein said cyano silver halide developing agent is positioned outside said silver halide emulsion layer.

12. A photosensitive element comprising a support carrying a photosensitive silver halide emulsion layer, a hydroquinone silver halide developing agent and an alkali hydrolyzable ester precursor of a cyano silver halide agent having the formula:

JJEN

bonded to a benzene ring.

13. The photosensitive element of claim 12 wherein said silver halide developing agent is of the formula:

RrQE-E-OH R EN References Cited UNITED STATES PATENTS 3,047,388 7/1962 Cairns 965 FOREIGN PATENTS 1,287,938 9/1972 Great Britain 9635.1

OTHER REFERENCES Chem. Absts., vol. 73, 1970, 612150.

NORMAN G. TORCHIN, Primary Examiner M. F. KELLY, Assistant Examiner US. Cl. X.R. 96-66.3, 

